COBRE LAS CRUCES
Production at Las Cruces decreased significantly compared to the first quarter of 2020, as mining activities at the operation ceased in August 2020 with ore depletion of Phase VI.
Las Cruces is a very high grade (5-6%) open-pit copper mine and hydrometallurgical plant located in the Sevilla Province of Southern Spain.
Overview
The hydrometallurgical plant relies on a unique atmospheric ferric leaching process to recover copper from the rich Las Cruces chalcocite ore. The process, specifically designed for Las Cruces polymetallic ore, is optimized to produce London Metal Exchange grade copper cathode with minimal water and energy use, controlled liquid effluent and a dry solid waste stream.
The plant is designed to produce approximately 72,000 tonnes of copper cathode per year which is shipped as final product.
Mining and Processing
The Las Cruces deposit is a polymetallic Volcanogenic Massive Sulphide deposit, similar to other Iberian Pyrite Belt deposits. A thick, high-grade supergene zone overlies the primary sulphides, comprised of a gold-bearing gossan zone in the upper part and a copper-rich secondary sulphide zone underneath.
Las Cruces uses conventional open pit mining methods, based on hydraulic excavators and trucks, with drilling and blasting in the lower marls and ore zones. Ore undergoes three stages of crushing, a single stage of grinding and is thickened to eliminate water before it goes to three pre-reactor tanks.
Eight Outotec OKTOP® agitated reactors dissolve the copper under conditions of high temperature and high acidity. Oxygen is also added into the reactors to complete the reaction.
Once leached, the liquid is separated from the ground solids, and the copper is recovered by the SX/EW process. The electrowinning cells produce London Metals Exchange grade copper cathodes weighing about 50kg each. An automated crane and stripping machine harvests and packages the cathodes for shipment.
Outlook
Research on the technical and economic feasibility of the polymetallic refinery project is progressing, as well as permits required to carry out this project in the medium term.
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